Knock Sensor: Description and Operation

Knock Sensor Location:

The knock control system allows calibration of the ignition timing for normal operating conditions, while eliminating the danger of knock or detonation due to influences by engine heat, load, fuel quality or engine deposits.

Knock Sensor Diagram:

The knock sensors consist of a housing and piezoelectric crystal between two connector strips mounted on a steel bushing. The sensors are located on the engine block (one sensor between #1 and #2 cylinders and one sensor between #3 and #4 cylinders) and are subjected to vibrations generated by knock (ping). The vibrations cause a small distortion on the surface of the piezoelectric crystal, generating a measureable voltage which is read by the CIS-E Motronic control unit. When the control unit recognizes a knock condition it will retard the ignition point for individual cylinders as necessary to eliminate the knock depending upon the intensity.